Automatic train-control system



April 13 1926. A

J. N. PAUL AUTOMATIC TRAIN CONTROL SYSTEM Filed July 7 1919 3 Sheets-Sheet 1' FIG. 1.

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J. N. PAUL AUTOMATIC TRAIN CONTROL SYSTEM Filed July '7 1919 3 Sheets-Sheet 2 F'GLS. 5

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' J. N. PAUL AUTOMATIC TRAIN CONTROL SYSTEM Filed July '7 1919 3 Sheets-Sheet 5 FIQH. HEW

W/ W BY W Y TORNEY.

Patented Apr. 13,1926.

UNITED STATES JOSEHH N. PAUL, OF ROCHESTER, NEW YORK, ASSIGNOR TO GENERAL RAILWAY SIGNAL COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

' AUTOMATIC TRAIN-CONTROL SYSTEM.

v Application filed July 7,

ToaZZ whom it may concern:

Be it known that I, JOSEPH N. PAUL, a citizen of the United' States, and resident of the city of Rochestenin the county of Monroe and State of New York, have invented a new and useful Automatic Train- Control System, of which the following is a specification. 3

This inventionv relates to automatic train control systems for railways, and more particularly to a means for transmitting controlling impulses or influences from the trackway to moving locomotives, motor cars or other railway vehicles, by electromagnetic induction, and without physical contact between any parts on the vehicles and parts along the track.

One object of my invention is to improve the operating characteristics of impulse transmitting means of the electromagnetic. type, so that the car-carried and the trackway impulse devices may be made more sensitive and reliable in their performance, may be reduced in size, and can be made so as not to be improperly afiected by track rails, or other magnetic bodies along the track. i

A further object is to provide an impulse transmitting means employing electromagnetic induction which will be accurately re-.. sponsive to the speed at which the vehicle passes the control points, and which can be rendered capable of acting at various selected speeds by constructing or adjusting either the trackway element or the car equipment. For-instance, my invention enables the desired impulse to be transmitted to a vehicle at any speed thereof above a predetermined minimum. k

A still further object is to provide impulse transmitting means of the inductive type in which the impulse received on the vehicle will be prolonged or drawn out, so to speak, so that effective and reliable operation of an ordinary relay may be obtained, without employing large or expensive trackway elements.

Generally stated, I attained these and other objects'by' utilizing the special elec trical characteristics of an amplifying and detecting relay device of the thermionic or vacuum bulb type, commonly known as an audion';

Other objects and specific features of my 1919. Serial No. 309,068.

invention will appear more fully hereinafter as the description progresses. i

In describing my invention i will 'refer to the accompanying drawing, in which are illustrated various embodiments of the invention, in which like reference characters refer to corresponding 'partsin the several views, and in which:

Figure 1 shows diagrammatically one arrangement of trackway circuits which may be employed in connection with the impulse transmitting means embodying'niy invention; Fig. 2 illustrates in a diagrammatic and simplified manner the construction and arrangement of the parts constituting the car equipment, together with the trackway element; Fig. 3 is a curve illustrating a typical operating characteristic of audions which is utilized in my invention; Fig. 1 shows a modified construction and arrangement of the car equipment; Fig.'- 5 is another curve of a characteristic of audions which illustrates the effect of cooling the filament upon the current in the plate circuit; Figs. 6 to 8 illustrate modifications of connections and arrangements of batteries for the car.

equipment; Fig. 9 illustrates a modified construction in which a permanent magnet is used for the trackway element; and Figs. 10 to 15 show further modifications of the car equipment.

The impulse transmitting means embodying my invention includes trackway elements which are governed in accordance with traffic conditions. Various arrangements of trackway circuits for governing these trackway elements may be employed; and the trackway circuits illustrated in; Fig.

11 detail I 1 are merely typical. Referring to Fig. 1,]

the track rails 1 of the railroad track are divided by insulated joints 2 into blocks in the usual way, one block I with the adjacent ends of two other blocks Hand J' being shown. The parts and circuits associated with the various blocks are the same, and for convenience will be given-like reference characters, with distinctive exponents. Each of the blocks is provided with a track battery 3 and a track relay 4, the; same as in ordinary block signal systems. My invention may be used with or without the usual fixed signals, depending upon the type of train control apparatus; and I have illustrated such fixed signals S conventionally,

without attempting to illustrate their .well known control circuits and devices.

The trackway element T of my invention in general comprises a magnetic yoke or. core and associated coils, and. is adapted to influence by electro-magnetic induction a cooperating element on a passing vehicle. In the construction illustrated, the trackway element T comprises a U-shaped core or yoke 5 provided with. pole pieces 6, and having coils 7 on its legs which are either oppositely wound or are wound in the same direction with diiferent number of turns.- These trackway elements T are intended to transmit controlling influences orimpulses to a passing train at one or more control points in each block, in accordance with traflic conditions in the next block in advance alone, or both the next block in advance and the corresponding block, depending upon the type of train control apparatus employed. In the trackway equipment shown in'Fig. 1, a trackway element .T is located at the entrance to each block, a short distance in the rear of the insulated joints 2, the normal direction oftrafiic being from left to right, as indicated by the arrow.

The coils 7 of each trackway element T are connected in series in a normally closed circu1t including the front contact of "a line relay 8. In the arrangement illustrated, the

controlling circuit for the line relay 8 includes a front contact of the trackrelay 4 of the corresponding block and a front contact of the track relay 4 of the next block in advance, so that the coils? of the track- Way element T at the entrance to each block are short-circuited under clear traflic conditions, but are open-circuited when either the corresponding block or the nextblock in advance is .occupied. The trackway. elements T may be located crosswise of the track between the .track rails (as shown in Fig. 1), or lengthwise, or outside of either track rail,.as preferred.

I prefer in practice to have the .upper faces ofthe pole pieces 6 of the trackway element- T as high as clearances on the particularrailroad equipped will permit; and in some instances I consider it desirable to locate the trackway elements outside of the track rails,s;ince there is more vertical clearancespace ordinarily available outside of use track 'rails than between them. It should be understood that other arrangements and constructions of trackwayelements may be employed, without departing from theessential features-of my invention.

The car-carried element L for cooperating (with the trackway element T, comprises. in general an inverted U-shaped magnetic core or yoke, provided with pole pieces, and-haw .in'g coils on its legs. This car-carried element L is supported in any suitable manner from the frame of .the locomotive or-otherapparatus or device.

vehicle, and is positioned thereon sothat'its pole pieces pass directly over the pole pieces (Ii of the trackway element T, as shown in 1g. 2. audion, employed in my invention, being well known, has been illustrated conventionally. This audion comprises a filament F, a grid G and a plate P. This audion is connected in circuit with suitable sources of current, the coils of the car-carried element L, and a control relay R, in any one of the various ways hereinafter described, so as to govern the operation of said control relay R in accordance with traflic conditions. 'The control relay R may be of any suitable type, but according to my investigations to date, I prefer a relay of the tractive type which is provided with a large number'of turns so as to be operable on small currents, 'and which has a laminated core, in order to be quick-acting.

. The control relay B may govern the operation of any suitable form of train control Since the particular type of train control apparatus forms no part of my invention, I have illustrated such device K conventionally as an electro-pneu-' matic valve, which may vent the train pipe and apply the brakes directly, or govern;

when the said control relay drops. In the construction illustrated, the dropping of the controlrelay R is only momentary, so that the train control device K, if continued operation thereof is required, must be provided with a stick circuit or other equivalent means, such as disclosed, for example, in .the application of Winthrop K. I-Iowe, Serial- No. 287,132, filed March 3, 1919, so that it will continue in operation after the control relay has picked up, so that, when once set into operation, it will continue in operationafter the control relay has picked up until restored manually or otherwise. Obviously, however, the control relay B may be a stick relay or may be provided with equivalent means.

The thermionic relay, device or v Referring first to the arrangement shown circuit of the audion, which includes a battery C. The filament F is heated in the usual way by a battery A. The control relay R is included in the plate circuit of the audion, and is normally energized from a battery B. The voltages of the batteries while'the car-carried element L is not pass ing over the trackway element suflicient currentflows' in the plate circult through the controlirelay R to close its contacts and are selected or adjusted so that normally,

maintain the train, control device K energized. For this purpose, I prefer to use a much lower voltage for the battery B in the plate circuit, than I understand has heretofore been ordinarily employed with audions in radio work, and the potential on the grid produced by the battery C is, I believe, higher than that ordinarily obtained in radio work. The voltages of the batteries A, -B and C will, of course, vary in practice, according to the type and operating characteristics of the audion, the control relay, and the electrical and magnetic characteristics of the trackway and car-car- One typical arrangement,

ried elements. which I found satisfactory sists of the battery A, 4 volts, battery B, 24 volts, battery C, 24 volts; but other combinations of batteries may be also used with satisfactory results.

The operation of the system shown in Fig. 2 will now be briefly described. Normally the current in the grid circuit through the coils 10 and 11 produces'a magneto-moti ve force sending flux through the yoke 9 of the car-carried element and through leakage paths around said yoke. In pracin practice, contice, with type of audion I have investigated,

this current is comparatively small, and the coils '10 and 11 must be wound accordingly. Underclear traffic conditions, the coils 7 of the trackway element T are short-circuited; and when the car-carried element L passes over the trackway element T in this safe controlling condition, the car equipment is not influenced sufiiciently to cause operation of the control relay R. I attribute this to the action of the short-circuited coils 7 of the trackway element T, which I believe choke back or oppose the passage of flux through the yoke 5 of the trackway element, thereby preventing any considerable change of flux through the coils 10 and 11 of the car-carried element L. Under dangerous trafiic conditions, the coils 7 of the trackway element T are open-circuited, so that thetrackway element presents in effect a dead magnetic loop to the car-carried element L on a passing vehicle. Thus, as the car-carried element L approaches and comes directly over the trackway elementT in this stopping condition, the reluctance of. the magnetic circuit through the coils 10 and 11 is greatly reduced, and the flux through the coils 10 and 11, due to the magneto-motive force produced by the current normally flowing in these coils, is increased. This increase in flux induces a counter E. M.'F. in the coils 10 and 11, which, in accordance with well known laws, opposes the battery 0, and reduces the potential of the grid G with respect to the potential of the filament The normal potential on the grid G being reduced, the current normally flowing in the plate circuit through the control relay R is likewise reduced, due to the well known characteristic of the audion. The parts are proportioned and adjusted so that the current-in the plate circuit is reduced in this way below the holdup value of the control relay B, so that its contacts open and de-energize the train 'control' device K, thereby placing the vehicle or train under the influence of the train control device K. As the car-carried element L passes away from the trackway element T,'the reluctance of the magnetic circuit through coils 10 and 11 is increased and the flux through these coils is consequently decreased. This decrease of flux induces an E. M. F. in coils 10 and 11 which aids the battery potential and so increases the positive potential of the grid G with respect to the potential of the filament F. This increase of normal grid potential will produce an increase in the current flowing in the plate circuit through the control relay R. Although thisincrease systems is that failure of any of the essential parts likely to break down 1npractice should be upon the side of safety. In the arrangement shown in Fig. 2, it will be observed that interruption of the circuit through the train control device K will set this device into operation. Likewise, in.- terruption of the plate circuit, or depreciation of the battery B, will tie-energize the control relay R, and thus set the train control device K into operation. Also, breaking of thefilament F, or depreciation of the battery A, 'reduces'the current in the plate circuit and causes the control relayK to open. If the battery C depreciat-es, or any part of the grid circuit opens, the current in the plate circuit through the control relay R .is reduced below the holdup value of said relay.

Fig. 3 illustrates a typical curve between plate current as ordinates and grid voltageas abscissa, the plate Voltage be ng maintained constant. From this curve it Wlll be observed that increase in grid voltage produces an increase in the plate current, until a certain value of grid voltage is rea lied, whereupon further increase 1n grid vo tage reduces the plate current at first and then,

when the grid voltage is carried to still higher values, there is littlechange in the plate current. In other words, t h1s curve has a knee or bend in it. The audion in my invention may be satisfactorily worked at any grid voltage below the knee of the curve; but I prefer to work at a high grid voltage beyond the knee of the curve as indicated, for example, at a point a. By working at this point a, a smallclecrease in grid voltage does not greatly reduce the plate current, in fact, increasing it first. This arrangement has the advantage of making the apparatus stable and not too sensitive for practical use, since the voltages ofthe batteries may vary within the limits ordinarily occurring in practice, without causing a premature or improper operation of the control relay.

Also, by working the audion at a grid voltage above the knee of the curve, I am able to employ that desirable type of trackway elements which, in the active or stopping condition, is in efi'ect an inert mass of iron, and at the same time I can obviate improper operation of the apparatus by the track rails at switches, crossover and other complicated track layouts, and also by other bodies of iron along the track, which may have a tendency to transmit a stopping impulse to a passing train in the same way as a trackway element. The influence of track rails and other foreign magnetic objects along the track upon the car-carried element, is much less than that obtained from a track- Way element, because the size and position of the track rails, and the like, does not make them as efficient a magnetic circuit. Consequently, the effect of the track rails upon the grid voltage is only a fraction of the effect produced by an active 'trackway element, that is, one having its coils open-circuited; and by properly proportioning and adjusting the parts and batteries, I.find that the apparatus may be worked at such a gridvoltage that the influence of track rails and other magnetic bodies ordinarily encountered along a railway track, will cause little, if any, decrease in the plate current, and will not, therefore, drop the control relay. This particular feature of my nvention is, of course, only necessary with lmpulse devices of the type in which the trackway element, when in the danger or stopping condition, merely constitutes a partial magnetic circuit.

In the modification of the car equipment illustrated in Fig. 4, two separate coils 12 and 13, connected in difierent circuits, are carried on the legs of the car-carried element L. One of these coils 12, which I term the field or primary coil, is connected in series with the filament F and battery A, and supplies the greater part of magnetomotive force for producing flux in the yoke 9 of the car-carried element. The other coil 13, which I term the inducing or secondary coil, is connected in the grid circuit and supplies some of the magneto-motive-force.

The modified arranglementof Fig. 4 has several advantages. he operation is in general similar to that already described in connection with Fig. 2. The potential induced in the secondary coil 13 by the track- "0 way element lowers the potentialv of the grid G, in the same wayas previously explained, to decrease the plate current. Also, for the same reasons, a counter E. M. F. is induced in the field coil 12 in opposition to the battery A. This momentarily reduces the voltage on the filament F and has the effect of partially cooling the filament. The effect produced upon the plate current by cooling the filament is illustrated by the curve in Fig. 5, which shows late current plotted as ordinates against filament current as abscissa, the plate voltage and grid voltage being constant. i From an inspectionof this, curve, it will be noted that a decrease in the filament current from any selected working value causes an amplified decrease in the plate current. In other words, the counter E. M. F. induced in the field coil 12 of the car-carried element L also tends to drop the 00 control relay R, due to the cooling of the filament. According to my investigations to date, I prefer to work the filament current at or just above the knee or bend in this curve, as indicated atthe point b, for the same reasons described, that is, in order to make the apparatus sufficiently stable for practical use and immune to the influence of track rails or the like. If desired, however, either or both the grid voltage or the filament current may be worked at high values; and in all cases the value of the filament current and grid voltage to be used in practice for the most effective results Will depend largely upon the type and characteristics of the audion, and also the magnetic and electrical characteristics of the various parts of the car equipment and the trackway element, so that no arbitrary values can be assigned.

This cooling of the filament, characteristic of the arrangement of Fig. 4, also has the advantage of prolonging or dragging out, so to' speak, the change in the plate current, perhaps because it takes an appreciable time for the filament to resume its normal working temperature, after having once been cooled. This prolonged change in the plate current produces a de-energizing influence upon the control relay R of sufficient duration to cause reliable operation thereof, even though the car-carried element passes very quickly over the trackway element, and even though the pole pieces of these respective elements are comparatively short. This permits the use of comparatively inexpensive and simple trackway elements and car-carried elements, and also obviates any need for extreme quick action on the part of the control relay.

Further regarding the arrangement shown in Fig. 4, I have found that the most efiicient results are obtained when the field coil 12 and the secondary coil 13 of the car-carried element Ii are wound in the proper direction and connected to the batteries A and C, so that the effect of reducing the potential of the grid by the E. M. F. induced in the secondary coil 13, and the effect of cooling the filament by the E. M. F. inducedin the field coil 12, will be cumulative and not opposing each other. This arrangement, however, is not compulsory and may be modified to suit varying requirements.

Another .feature of the arrangement illustrated in Fig. 4 is that the primary or field coil 12 is connected in series with the filament. Thus, if the circuit through the field coil 12 should break, the filament will cool and the control relay will drop, thereby detecting the failure. Also, if a cross occurs so as to short-circuit the field coil 12, the voltage applied to the filament F is greatly increased, due to cutting out the voltage drop through the field coil 12. By properly selecting the resistances and voltages, this increase in voltage'due to short-clrcuiting the field coil 12 may beso great as to burn out the filament F, which will also cause the control relay R to drop. Moreover, if the field coil 12 is shunted out, the average potential of the filament F with respect to the grid G is increased, thereby in turn decreasing the plate current and causing the control relay R to drop. To explain more fully, assume the battery A to be 12 volts, and that there is an 8 volt drop in the field coil 12. Then, there are 4 volts across the filament F, and the average potential of the filament is two volts higher than its negative end which 13 connected to the grid circuit. If, now, a cross occurs to shunt out the field coil 12, the full voltage of the battery A is applied to the filament, increasing its average potential to six volts above its negative end, or four volts greater than the normal difference in potential between the grid and the filament. This is equivalent to reducing the grid potential with respect to the filament, and this causes the control relay to drop. These voltages are merely selected for purposes of illustration, and are subject to variatlon in practice. The protection against failure of the other circuits is the same as previously described, and likewise the modifioation of Fig. 4 may be selected and proportioned so as not to be improperly infiuenced by track rails or the like.

Fig. 6 illustrates a modification of the arrangement shown in Fig. 4. In this modification provision is made to detect and guard the apparatus against a cross shortcircuiting the inducing or secondary coil. This is accomplished by employing a detecting device responsive to the flux which is produced by the secondary coil 13, so that,

nnless said coil is connected properly in the grid circuit and is energized by the battery the detecting device will operate. In the simplified construction illustrated, this magnetic detector comprises an armature 15 which is pivotally supported at its lower end on the pole piece below the coil 13, and which is normally attracted by the flux produced by said coil against a residual pin of a projection 16 from the leg of the yoke 9 above said coil. This armature 15 is biased to the open position by a spring 17 and carries an insulated contact piece 18 adapted to make contact with suitable fixed contacts (indicated conventionally as arrows), which are included in the circuit for the train control device K. It will be evident that so long as flux is produced in the yoke 9, some of it will pass through the armature 15 and maintain it closed. This flux in the yoke 9 is produced partly by'the field coil 12 and partly by the secondary coil 13; and the armature 15 may be designed and adjusted so that it will be attracted so long as both of these coils 12 and 13 are fully and prop erly energized, but will be pulled away by the s ring 17 and set the train control device li into operation, whenever current ceases to flow through either or bothof these coils 12 and 13. For example, assuming the coils 12 and 13 to have equal ampere turns, the armature 15 should be adjusted so as to pull away upon a reduction of approximately' one-half in the flux normally passing through it. In this connection it should be noted that not all of the flux produced by the field coil 12 will pass through the righthand leg of the yoke 9, some of this flux' being d1- verted to leakage paths; and consequently, even if the ampere turns of the coils 12 and 13 are e ual, the coil 13 will predominate in its inl uence upon the armature l5. Obviously, the armature 15 may be associated with any part of the magnetic circuitthrough the coils 12 and 13; and the same armature may be used to detect failure of current through either coil, or separate armatures may be used for detecting failure of the current through the coils individually. Since failure of current through the field coil 12 is automatically detected by yirtue of its connection into the filament clrcuit, as previously explained, I prefer in most n stances the arrangement illustrated in Fig. 6, Where the armature 15 is primarily under the influence of the secondary coil 13. The contacts 18 controlled by the armature 15 may be included in any one of the other circuits of the equipment, the lnterruption of which results in operating the train control device K.

Fig. 7 illustrates a modified arrangement of circuits in .whichthe batteries A and C of Fig. 4 are combined in a single battery.

Fig. 8 illustrates a similar arrangement,

in which the batteries A and C are combined, and in which the difference of potential between the filament F and the grid G is produeed by the Voltage drop through the filament F1 Fig. 9 illustrates a modified construction in which a permanent magnet is employed with the trackway'element, the car equipment illustrated being the same as that that is, when the line relay 8 is picked ups The coils 23 are so wound and connected wlth the battery 24 that the, magneto-motive force produced thereby opposes that of thepermanent magnet 20, thereby diverting the greater portion of the permanent flux through the leakage paths, so that the magnetic field above the pole pieces 21 of the trackway element T is very weak. Under dangerous trafiic conditions, the coils 23 are open-circuited, so that the full strength of braces the yoke 9 on a passing car. Change of flux through the yoke 9 of the car-carried element induces an E. M. F. in the coils 10 and 11, and these coils are so wound, that the E. M. F. induced therein reduces the grid potential, thereby causing operation of the control relay R in the same way as previousl explained. The battery C illustrated in ig. 9 in the grid circuit is employed to maintain normally a difference of potential between the filament and the grid.

Fig. 10 illustrates an arrangement employing only the filament F and plate P of the audion, and operating by virtue of the eflect produced on the late current by coo1- ing the filament F. n this arrangement, the filament F is connected in series with the two coils 10 and '11 on the legs of the carcarried element. Normally, the temperature of the filament, and the voltage in the plate circuit, are such as to permit sufiicient current in the plate circuit to maintain the control relay energized. When the car-carried element passes over an active trackway element, the counter E. M. F. induced in the coils 10 and 11 opposes the battery C and cools the filament F to the point where the current in the plate circuit is decreased below the holdup value of the control relay. B.

Fig. 11 illustrates a still furthermodification in which the field coil; 12 of the ,car-

carried element is energizedfrom' a battery 25 wholly disconnected from the audion' or other devices. Anarmature-1'5}, similar to that shown in Fig. 6, previously described, is prefer-ably employed in connection with the field coil 12 to detect any failure thereof. If desired, the secondary coll 13 may be provided with a similar detecting armature. In other respects this arrangement operates in the same manner as previously described.

Fig. 12 illustrates an arrangement in which a permanent magnet 26 is used on the car to produce the flux which is changed as the car passes over an active trackway element of the type shown in Fig. 2. The coils 10 and 11 on the legs of the permanent magnet 26 are connected in the grid circuit in the arrangement illustrated, the same as shown in Fig. 2; but any of the other various connections previously described may be employed, if desired, the permanent magnet constituting merely a substitute source of magneto-motive force, or an additional source, as the case may be, for producing the change of flux in the secondary coil of the car-carried element. The car equipment of Fig. 12 may also be used with the trackway element shown in Fig. 9, if desired, the polarity of the respective permanent magnets on the car and on the track being arranged such that these magnets act together to send flux through the secondary coils 10 and 11. the magnet1c field of the permanent magnet 20 appears above the pole pieces 21 and em Fig. 13 illustrates an arrangement of circuits, similar to that shown in Fig. 4, in which a single battery, or strictly speaking,

two sections 27 and 28 of a battery, are employed for the filament, grid and plate circuits. The operation of this modification,- together with its features of protection, are the same as already described. The two sections 27 and 28 of the battery constitute the batteries B and C of Fig. 4, and the section 28 constitutes the battery A of Fig. 4. The energy demands upon these two sections are, according to my investigations, different and the number of cells included in these sections may be selected according to the energy demands. I prefer, however, to employ two sections of battery of the same voltage and capacity, and employ a change-over switch M, as shown in Fig. 14, so that these sections 27 and 28 may be used alternately in the filament circuit. The winding of the field coil 12 can be proportioned so that the same battery may be used in the filament circuit, instead of a section of battery, thereby energizing all circuits from the same batter Fig. 15 shows one construction of car equipment in which alternating current is employed instead of direct current obtalned from batteries. This alternating current may be obtained onthe car from any suitable- ,source, as a motor generator driven from storage-batteries, or, in the case of a 1000- .motive,'- from a steam driven generator, such as is now commonly used jt'ogenerate currentforfhead lightst I use a:transformer 30 in the usual manner to obtain the desired 12 and the secondary coil 13. The plate cir-- cuit is connected in the same way as previously described.

The operation of this modification is substantially the same as previously explained. The alternating current, being derived from the same source, will change polarity at the same instant in the various circuits, so that the relative potentials in these circuits at every instant will be the same as if batteries were used. One important feature ofthis construction is the fact that failureof the secondary coil 13, as well as the field coil 12, is automatically detected. The E. M. F. in the grid circuit including the secondary coil 13 is derived by transformer action, and consequently, if the secondary coil is open-circuited, 'or short-circuited by a break or cross, the grid voltage decreases or falls to zero thereby causing the control relay to open.

One important characteristic of my invention is the fact that the apparatus may be proportioned or adjusted so that the control relay will be operated when the car passes a track'wa element in the danger position at any spee above a selected minimum; In

7 other words, the efiect of transmission of the 'that this is substantially true.

impulse in accordance with my invention is accurately dependent upon the speed of the car. I attribute this to the fact that the audion is essentially a device responding to voltage or potential changes more than to current changes. The voltage induced in a coil on a car while passing over a trackway element, whether the flux is transmitted from the trackway or from the car, is theoretically,

I believe, almost exactly in proportion to the speed of the car, and investigations indicate However,

when it is attempted to detect this induced voltage by the operation of a relay connected to the coil, it is found that, for some reason, perhaps on account of the inductance of the coil and its associated relay, the current produced in the relay, while dependent to some extent upon speed, does not vary through wide enough limits, or accurately enough, to make the relay reliably responsive according to different speeds of thecar. According to my invention, however, the car equipment may be made responsive to speed within as narrow limits as desired; and without undue refinement, may be made to act within a range of one or two miles per hour at any speed above any desired or fixed minimum.

The hunting minimum speed at which the control relay It in my invention will operate, is dependent upon a number of factors,

any one of which may be used as a basis for varying this critical speed. An audion of different characteristics, a change in the voltages of the several batteries, variation in the operating characteristics of the conti'ol'relay, change in the air gaps between the car-carried element and the trackway element, a change in the amount and disposition of the windings of the coils of the carcarried element, a change in the size or cross section of the car-carried element or trackway element, all vary to a more or less degree the criticalliiiiiting speed atv which the control relay will drop, Any one of these various factors may be modified, either on the track or on the train, to apply the im pulse transmitting means embodying my in vention to a system of speed control for trains, that is, a system in which the speed of vehicles is regulated in accordance-With traffic conditions in a predetermined manner.

In describing the invention, I have outlined-some of the forms which the car equipment and trackway equipment may take but it should be understood that the modificatioiis illustrated do not exhaust all of the various embodiments of. my invention. Various types of car-carried and trackway elements may be employed in my invention, the only essential requisite being that these elements shall cooperate to produce an induced voltage on the car by electro-magnetic induction from the trackway under dangerous traflic conditions, and not under clear traflic conditions. Obviously, this essential requirement maybe satisfied in various ways, some of whichhave been illustrated. The electro-motive force causing the change of flux in the coilor winding on the car may be derived from a source on the car, as in Fig.. 4, for example, or from a source on the track, as in Fig. 9 for example. I prefer a. trackway element of the type shown in Fig. 2 because of its simplicity and cheapness; and while a battery or other source of current on the track may be used in the circuit for the coil 7 to produce a magneto-motive force opposing that of the car-carriedvelement and thus provide the proceed indication, I prefer the arrangement illustrated, because it obviates the complications incident to the use of trackway batteries, and also the cost of their care and maintenance.

Furthermore, various modifications and adaptations of the audion and its connections to the coils of the car-carried element, other than those illustrated, may be employed without departing from my invention. For example, two or more audions, coupled in cascade, may be employed, if desired. Various connections of batteries or other sources of current to the coils and the elements of the audion may be used, provided the appropriate potentials upon the filament, grid and plate of the audion are obtained. For example, referring to Fig. 2, the voltage of the battery A is shown as adding to the voltages of the batteries I; and C, but the connections may be arranged so that the battery A opposes either or both of the batteries l3 and C. p

I desire to have it understood, therefore, that the specific embodiments of my invention shown and described are merely illustrative, and do not exhaust the modifications of the idea of means and the functions thereof constituting my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. Impulse transmitting means for automatic train control systems comprising a trackway element having its magnetic condition governed in accordance with traffic conditions in advance, acar-carried element including a coil and adapted to cooperate with said trackway element to cause voltage to be induced in said coil under dangerous traflic conditions, train control means on the car, and a thermionic relay responsive to I the voltage induced in said coil for govern.

ing said train control means.

2. In an automatictrain control system for railroads having tracks divided into blocks each provided with a normally closed track circuit, a trackway element associated with each block and having its magnetic condition controlled by the track relay of the block next in advance, a car-carried element cooperating electro-magnetically with said trackway element, train control means on a car, and a thermionic relay on the car responsive to the cooperation of the car-carried element with a trackway element for.

governing said train control means.

3. In an automatic train control system, impulse transmitting means comprising, a car-carried element including a coil, trackway elements adapted when in the active stopping condition to cause voltage to be induced in said coil, and an audion for detecting said induced voltage.

4. In an automatic train control system, a car-carried circuit, traifie controlled means partly on the car and partly on the track for causing voltage to be induced in said circuit under dangerous traflic conditions, train control means on the car, and a thermionic relay responsive to the voltage induced in said circuit for governing the operation of said train control means.

5. In an automatic train control system,

means for communicating electromagnetic impulses or influences between the trackway and moving vehicles comprising a car-carried circuit, means partly on the vehicle and partly along the track for causing voltage variations in said circuit, and means including an audion for detecting said voltage variations, said audion being normally worked at a relatively hight grid voltage.

(3. In an automatic train control system, means for communicating electromagnetic impulses or influences between the trackway and moving vehicles comprising a car-carried circuit, means partly on the vehicle and partly along the track for causin voltage variations in said circuit, an an ion having its grid potential modified by the voltage variations in said car-carried circuit, and a relay included in the plate circuit of the audion, the constants of said audion and the voltages used therewith being of such values that a small change in grid potential will produce no change in plate current while a larger change in grid potential will cause a large change in plate current.

7. In an automatic train control system, means for establishing communication between the trackway and moving vehicles, comprising an audion on the vehicle, electroresponsive means included in the plate circuitof the audion, and traflic controlled means partly on the vehicle and partly along the track for varying the temperature of the filament of said audion.

8. Impulse transmitting means for automatic train control systems comprising, in combination, a coil on the vehicle, means partly on the vehicle and partly along the track for causing voltage variations in said coil under dangerous trafiic conditions, tram control means on the vehicle, and an audion responsive to said induced voltage for governing the operation of said train control means.

9. Impulse transmitting means for automatic train control systems comprising, a car-carried circuit and cooperating means on the trackway effective to produce an induced voltage in a coil on the car which varies in strength in accordance with the speed of the car, a thermionic relay influenced by said induced voltage, and electroresponslve means on the car controlled by said relay.

10. Impulse transmitting means for automatic train control systems responsive to the speed of a vehicle comprising, means acting to produce an induced voltage in a circult on a car which varies in accordance with the speed of the car at predetermined control pO1I1tS 3.Ild means iricluding a thermionic relay for detecting the variations in said induced voltage.

11. In an automatic train controlfsystem, impulse transmitting means comprising a .and a secondary coil, a trackway element adapted when in the active or stopping condition to complete the partial magnetic circuit of the car-carried yoke, an audion having its filament connected in circuit with the field coil and its grid circuit connected to,

the secondary coil, and a control relay connected in the plate circuit of the audion.

13. In an automatic train control system,

impulse transmitting means comprising a trackway element including a magnetic yoke and coils, trafiic controlled means for con-- trolling the circuit of the coils of said track- Way element, a car-carried element compris- 1ng a magnetic yoke and having a field coil and a secondary coil, a source of magnetomotive force for the car-carried yoke, an audion having its filament connected in circuit with the field coil and its grid connected in circuit with the secondary coil, a control relay included in the plate circuit of the audion, and means on the vehicle 'for supplying energy to the circuits of the audion.

14,. In an automatic train control system for railway vehicles, a normally energized electro-responsivc device on the vehicle, adapted when deenergized to cause automatic control of'the vehicle, an audion controlling said device, means on the vehicle for normally maintaining a uni-directional potential on the grid of said audion and thereby maintaining energization of said de vice, and traffic controlled means for changing the amplitude of said grid potential to cause deenergization of said device.

15. In an automatic train control system for railway vehicles, normally energized train control apparatus on the vehicle, and means for causing deenergization of said apparatus at control points along the track comprising an audion, the grid circuit of which is maintained energized by a uni-directional potential and car-carried and trackway elements cooperating inductively through an intervening air-gap.

16. Car equipment for automatic train control systems comprising anaudion, a relay connected in the plate circuit of the audion, a car-carried circuit for normally maintaining a uni-directional potential on the grid of the audion, and traflic controlled trackway means acting to reduce said grid potential and thereby causing deenergization of said relay.

, 17. In an automatic train control system, train control apparatus on a vehicle including a thermionic relay, an input circuit for said relay including a source of uni-directional potential, and means partly on the track and partly on the vehicle for influencing said input circuit at selected control points along the track.

18. In an automatic train control system, impulse transmitting means comprising an audion on a vehicle, a circuit on the vehicle including a source of current for heating the filament of the audion, a coil in said-circuit, and means for producing voltage variations in said coil at control points along said track. 7 4

19. In an automatic train control system, brake control apparatus on a car, control means on the car for initiating operation of said apparatus and comprising a group of normally energized devices and circuits, said control means including a control relay of'the tractive type and a vacuum tube amplifier said control relay being included in the plate circuit of said amplifier, a circuit and a source of electricity constantly applying a uni-directionalpotential tothe grid of said amplifier, and means comprising cooperating car-carried and track elements adapted to act intermittently at selected control points along the track for influencing said circuit only under dangerous traflic conditions to vary the potential applied to the grid of the amplifier and thereby cause effective deenergization of the control relay and operation of said apparatus.

20. In an automatic traincontrol system, impulse transmitting means I comprising track elements acting as a mass of iron when in the active stopping condition, and car equipment including an electro-responsive device of the audion type having a grid circuit normally energized from a source of uni-directional potential, said circuit being influenced by said track elements in the active condition.

21. Impulse transmitting means for automatic train control systems comprising a partial magnetic circuit on a vehicle, trackway means for changing the reluctance of said circuit, a coil associated with said circuit, and means including a thermionic relay of the audion type having a grid circuit normally energized by a uni-directional potential, said grid,circuit being responsive to voltage variations in said coil.

22. Impulse transmitting means for automatic train control systems comprising a partial magnetic circuit on a vehicle, trackway means for intermittently influencing said circuit, and means 'including a thermionic relay of the audion type having a grid circuit normally energized by a uni- '25 trol apparatus on a vehicle, control means therefor mcluding an amplifier, and car car-;:

'05 audion controlling said apparatus,

directional potential, said grid circuit being responsive toflux variations-m said magnetrc circuit.

23. Car equipment for automatic train -5 control systems comprising an energized partial magnetic circuit, a. coil associated with said circuit, an electro-responsive device of the audion type having its input circuit normally energized by a uni-directional 1o potential' and connected to. said coil, .and

train control means governed by the output circuit of said device.

24. In an automatic train control system,

brake control apparatus on a vehicle, amphfying means for governing said apparatus duced voltage in said input-circuit to neu? tralize partially the voltage-of, said source and cause actuation of the rake controlapparatus.

25. In a train control system, con:

ried and track elements cooperating through an intervening air gap for governin said control means, said track' elements'eac come prising a non-magnetized mass of iron anda winding in magnetic circuit therewith, said w nding being automatically placed on open circuit under dangerous trafiic conditions and bein included in a closed deenergzed circuit 0 low resistance under clear traflic conditions.

26. In a train control system, brake control apparatus on a vehicle, control means therefor including an amplifier and a normally closed circuit energized with uni-directional voltage, and means'partly on the vehicle and partly on the track and includmg cooperatmg partial magneticcircuits for producing voltage changes in said circuit in partial opposition to its energizing voltage and thereby causing operation of the brake control apparatus.

27. In a train control .sytsem, the combination with a car carried element consituting 6 a partial magnetic c1rcu1t, means for maintaining in said magnetic circuit a uni-directional flux, and trackway means for varying the reluctance of said circuit, of train control apparatus on the car including amplifying means and responsive to flux variations 1n said partial magnetic circuit.

' 28. Car apparatus comprising a magnetic core, a coil thereon, a clrcuit including said coil and a source of direct current, tram con- I trol apparatus, and amplifying means responsive to potential changes in said circuit for governing said apparatus.

29. A tram control system comprising, brake governing apparatus on a vehicle, an a circuit including a coil and a source of electrical energy for normally maintainin a uni-directional potential on the -grid of the audion, and means partly on the vehicle and partly on the track for producing voltage changes in said coil.

30. In a train control system in which conin said coil andv control circuit, and other me'ans responsive to the flux produced by the "coil for checking the integrity of the control circuit. 1 31.11

a train control system in which controlling influences are communciated from the trackwayto moving vehicles by electro- Zma etic induction, tram control apparatus an governing means therefor compris ng a normally energized circuit and amplifying means, and biased circuit controlling means independent of said overning means and operated by flux pro need by the flow of current in said circuit for detecting interruption of said circuit.

32. In a train control system in which controlling influences are communicated from the trackway to moving vehicles by electroma etic induction, a control relay and an an 'on governing said relay and having unidirectional potential normally mamtamed on its grid by a source of cur-rent on the vehicle. 33. In a train control system in which controlling influences are communicated Irom the trackway to moving veh1c1es by electromagnetic induction, 1n combmation with trackelements constituting an inert mass of iron when in the active stopping condition, a coil normally energized by a uni-directional potential in which potential changes are produced during the passage of the vehicle ,by said track elements, a relay of the 'tractive type normally energ1z ed by direct current, and'means for amplifying such potential changes and utilizing them to moving vehicle through an intervening airgap by the transfer of magnetlc flux, the combination with brake control apparatus on the vehicle, of a normally energized relay of the tractive type maintaining said apparatus inactive, a track element havlng an iron core and a winding magnetically associated with said core, track circuit controlled means for placing said winding on open c1rcuit under dangerous traflic conditlons and for including said winding in a closed deenergized circuit under safe traflic conditions, a car-carried core with a coil thereon adapted to cooperate with said track element, an amplifier of the vacuum tube type electrically connecting said coil and said relay, and a source of direct current maintaining said coil and amplifier energized,

36. Car carried impulse receiving means for train control systems. comprising, an audion, brake control apparatus normally maintained inactive by potential on the grid of said audion, and means adapted to be influenced from the trackway for varying the grid potential of the audion, said means including an energized coil connected in series with the filament of the audion.

37. In a system for controlling relays on railway vehicles inductively by exchange of flux between the vehicle and the trackway, means partly on the vehicle and partly on the track constituting two cooperating partial magnetic circuits, a source of magnetomotive-force for the completed magnetic circuit formed by said partial circuits, traflic controlled means'on the track for opposing the passage of flux through said completed magnetic circuit, a receiving coil on the vehicle responsive to a change in the flux through the partial circuit on the vehicle, and an audion connected to said receiving coil and controlling the train control relay.

38. Car-carried apparatus for automatic train control systems comprising, a car element of magnetic material having a normally energized field coil and a secondary coil thereon, means connected to said secondary coil for detecting sudden changes of flux therethrough, and other meansfor detecting a failure of flux through said secondary coil. 39. In a system for controlling the brakes of railway vehicles by influences transmittedinductively from the trackway to car-carried devices comprising, a car element including a normally energized field coil and a secondary coil, athermionic device'having a filament, a grid and a plate, a circuit for said filament including said source of energy, a circuit for said grid in; cluding said secondary coil, and a circuit. for.

field coil anda various constants of said thermionic device being so adjusted that either a decrease of current in said filament or a decrease of po-, tential on said grid will cause a decrease of current in said plate circuit.

40. Car-carried apparatus for train confield coil decreases to a predetermined extent, or when a sudden change of flux through the secondary coil takes place, and other means for deenergizing said brake control device when the flux through said secondary coil falls to a predetermined value.

41. Car-carried apparatus for automatic train control systems comprising, a yoke of magnetic material having a downwardly extending leg normally magnetized by uni-directional magneto-motive-force, a coil on said leg for detecting a rapid change of flux therethrough, and flux responsive means associated with said yoke for detecting thefailure of such flux.

42. Influence transmitting means for transmitting control influences from the trackway to a moving vehicle for train control systems comprising, an audion provided with the usual filament, plate and grid, a plate circuit for the audion including a source of energy and a normally energized electro-responsive device, and means partly along the track and partly on the vehicle for simultaneously varying the temperature of the filament and the potential impressed upon the grid of said audion, whereby a eumulative. influence will be transmitted to said electro-responsive device.

43.,In an automatic train control system, the combination of brake control apparatus on a vehicle and of control means upon the vehicle for initiating operation of said apparatus comprising, a core of magnetic material, a field coil for producing a magnetomotive-force'in said core, a secondary coil on said core, and means including an audion cumulativelyresponsive to a decrease of current'inls'aidfield coil and to a changeof flux.

through said secondary coil for initiating operat1o nf .of sai d brake control apparatus;

said plate including a source o'f n gy, ,,;;e-=

the current in the energizing circuit for the 

